High-pressure pump having small initial axial force of a clamping bolt

ABSTRACT

A high pressure pump for preventing distortion of a sealing surface or a cylinder form. The high pressure pump has an intermediate member including a cylinder body having a pressurizing chamber communicated with a cylinder accommodating a plunger. Fluid in the pressurizing chamber is pressurized by reciprocating the plunger. The intermediate member is arranged between a cover and a flange and is clamped by clamping bolts. An electromagnetic spill valve for receiving reaction force from the pressurizing chamber when the fluid in the pressurizing chamber is pressurized is attached to the cover at a position for reducing the clamping force applied to the intermediate member by the clamping bolts.

BACKGROUND OF THE INVENTION

The present invention relates to a high pressure pump, and moreparticularly, to a high pressure pump having an intermediate member,which includes a cylinder body to pressurize fluid in a pressurizingchamber by reciprocating a plunger in a cylinder and which is arrangedbetween two clamping members, the intermediate member being clamped by aclamping bolt, which extends between the two clamping members, by meansof the clamping members.

For example, Japanese Laid-Open Patent Publication No. 11-210598discloses a high pressure fuel pump used for an engine such as acylinder injection type gasoline engine. In the high pressure fuel pump,to improve the machining characteristics and assembling characteristics,an intermediate member such as a sleeve (corresponding to cylinder body)is clamped between members such as a bracket along the axial directionand fastened to a casing by a clamping bolt.

Further, in the high pressure fuel pump, if the sleeve is just clamped,its cylinder form tends to be easily deformed. Therefore, a slit isformed between a clamping portion of the sleeve and the cylinder. Theslit prevents the deformation caused by clamping cylindrical clampingmembers from affecting the cylinder form.

However, the clamping bolt for clamping the sleeve requires a relativelylarge initial, axial force. This is because the initial, axial forceincludes not only the axial force required for sealing the intermediatemember but also requires the axial force required for coping withchanges in the axial force resulting from fuel pressure pulsation thatis produced when the high pressure pump is activated. Therefore, takinginto consideration the change in the axial force of the high pressurepump, the intermediate member must be clamped with a relatively largeinitial, axial force when manufactured. However, when the intermediatemember is clamped by a large initial, axial force with the clampingbolt, deformation of a sealing surface of the intermediate member ordeformation of the cylinder form occurs. It is difficult to prevent suchdistortion.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a high pressure pumpand a coupling structure of a high pressure pump having small initialaxial force of a clamping bolt and being capable of preventingdistortion of a sealing surface or a cylinder form.

One aspect of the present invention provides a high pressure pump havingan intermediate member including a cylinder body having a pressurizingchamber communicated with a cylinder accommodating a plunger. Fluid inthe pressurizing chamber is pressurized by reciprocating the plunger.The high pressure pump includes two clamping members arranged on twosides of the intermediate member, a clamping bolt extending between thetwo clamping members to clamp the intermediate member with the twoclamping members, and a member for receiving reaction force from thepressurizing chamber when the fluid in the pressurizing chamber ispressurized. The member for receiving the reaction force is attached toone of the two clamping members at a position for reducing the clampingforce applied to the intermediate member by the clamping bolt.

In this structure, the member for receiving the reaction force isattached so that the reaction force of the pressurizing chamber isapplied to the clamping member to reduce the clamping force applied tothe intermediate member. Therefore, even if the reaction force of thepressurizing chamber, which is produced by fluid pressure pulsationduring operation of the high pressure pump, is applied to the clampingmember, the member for receiving the reaction force decreases thereaction force produced by the clamping of the intermediate member.Accordingly, the total reaction force becomes smaller than a sum of thereaction force of the pressurizing chamber and the reaction forceproduced when by clamping the intermediate member. The change of axialforce caused by the fluid pressure pulsation during operation of thehigh pressure pump decreases. As a result, the initial axial force isdecreased, and distortion of a sealing surface or a cylinder form isprevented.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1(A) is a schematic diagram of a high pressure pump according tothe present invention in a stationary state, and FIG. 1(B) is aschematic diagram of a prior art high pressure pump in an stationarystate.

FIG. 2(A) is a schematic diagram of a high pressure pump according tothe present invention in a dynamic state, and FIG. 2(B) is a schematicdiagram of a prior art high pressure fuel pump in a dynamic state.

FIG. 3 is a cross sectional view of a high pressure pump according to anembodiment of the present invention.

FIG. 4 is a schematic diagram of a fuel supplying system for an internalcombustion engine incorporating the high pressure fuel pump.

FIG. 5 is a cross sectional view of a high pressure pump according to anembodiment of the present invention.

DETAILED DESCRIPTION

Before describing a high pressure pump according to an embodiment of thepresent invention, the principle of the present invention will bediscussed. In the high pressure pump of the present invention, which isschematically shown in FIG. 1(A), an intermediate member M including acylinder body is arranged between two clamping members E1, E2. Theintermediate member M is clamped between the clamping members E1, E2 byclamping bolts B1, B2, which extend between the clamping members E1, E2.A member G is attached the clamping member E1 on the side that isopposite to the side where the intermediate member M is clamped. Whenfluid in a pressurizing chamber I is compressed by a plunger D andpressurized, the member G receives reaction force from the pressurizingchamber I.

In the high pressure pump of FIG. 1(A), when the intermediate member Mis clamped by the clamping bolts B1, B2, the intermediate member M iselastically deformed and reaction force F0 is generated. Therelationship between the reaction force F0 and the axial force Bfproduced by the clamping bolts B1, B2 is represented by the followingequation [1].F0=2·Bf  [1]

In a prior art high pressure pump, which is shown in FIG. 1(B), whenfluid is compressed and pressurized in a pressurizing chamber I by aplunger d, a member g receives reaction force from the pressurizingchamber i. The member g and intermediate members m1, m2 are arrangedbetween two clamping members e1, e2. In this case, when the intermediatemembers m1, m2 and the member g are clamped by the clamping bolts b1,b2, the intermediate members m1, m2 and the member g are elasticallydeformed and the reaction force F0 is generated. The relationshipbetween the clamping bolts b1, b2 and the axial force bf is representedby the following equation [2].F0=2·bf  [2]

Accordingly, the relationship between the reaction force f0 and theaxial force is the same in equations [1] and [2]. Therefore, intightening when the high pressure pump stops, the axial force Bf of theclamping bolts B1, B2 of FIG. 1(A) is set same as the axial force bf ofthe clamping bolts b1, b2 of FIG. 1(B).

However, when reaction force FN is generated as the pressurizing chamberI is pressurized, the member G receives the reaction force FN from thepressurizing chamber I in the high pressure pump of the presentinvention shown in FIG. 2(A). Because the member G is arranged on theside opposite to the clamping side of the intermediate member M, thereaction force FN acts as a lifting force FU applied to the clampingmember E1. The lifting force FU is an element of the axial force Bfgenerated at the clamping bolts B1, B2. Another element of the axialforce Bf is reaction force FM from the intermediate member M. Therefore,the axial force Bf is represented by the following equation [3].2·Bf=FU+FM  [3]

The reaction force FM from the intermediate member M decreases theclamping force applied to the intermediate member M in accordance withthe amount the clamping member E1 is lifted by the lifting force FU.This decreases the compression amount of the intermediate member M.Thus, the reaction force FM is smaller than the reaction force F0 ofFIG. 1(A).

On the other hand, in the high pressure pump of the prior art shown inFIG. 2(B), the member g that receives the reaction force FN from thepressurizing chamber I is arranged on the clamping side with theintermediate members m1, m2. In this case, the generated lifting forceFU of the clamping member e1 resulting from the reaction force FN is anelement of the axial force bf generated at the clamping bolts b1, b2.Another element of the axial force bf is the reaction force Fm from theintermediate members m1, m2 and the element g. Therefore, the axialforce bf is represented by the following equation [4].2·bf=FU+Fm  [4]

The member g is arranged together with the intermediate member m1between the clamping member e1 and the pressurizing chamber i. Thiscauses the reaction force FN to increase the compression amount of themember g and the intermediate member m1. Therefore, the reaction forceis almost same as the reaction force F0 in FIG. 1(B). Even if thereaction force FN decreases, the decreased degree is less than thedifference between the reaction force F0 in FIG. 1(A) and the reactionforce FM in FIG. 2(A). That is, FM<Fm. Therefore, in the state of FIGS.2(A) and 2(B), Bf<bf is satisfied. As a result, in the high pressurepump of the present invention, when fluid in the pressurizing chamber ispressurized, an increase in the axial force of the clamping bolt isincreased by the reaction force received from the pressurizing chamber.In other words, change in the axial force caused by fluid pressurepulsation during operation of the high pressure pump decreases. Thisenables the initial axial force of the clamping bolt to be relativelysmall. Therefore, the sealing surface and the cylinder form areprevented from being distorted.

FIG. 3 is a cross sectional view of a high pressure fuel pump 2according to one embodiment of the present invention. The high pressurefuel pump 2 is incorporated in a cylinder injection type gasoline engineE, as shown in FIG. 4, and generates high pressure fuel injected intocombustion chambers of the engine E.

As shown in FIG. 3, the high pressure fuel pump 2 has a cylinder body 4,a cover 6, a flange 8 and an electromagnetic spill valve 10. A cylinder4 a is formed along the axis of the cylinder body 4. A plunger 12 issupported in the cylinder 4 a slidably in the axial direction. Apressurizing chamber 14, which is communicated with the cylinder 4 a, isdefined at the distal side of the cylinder 4 a in the cylinder body 4. Avolume of the pressurizing chamber 14 is varied as the plunger 12 movesinto or out of the pressurizing chamber 14.

The pressurizing chamber 14 is connected to a check valve 18 via a fuelpressure supply passage 16. The check valve 18 is connected to a fueldistribution pipe 20 (FIG. 4). The check valve 18 is opened when thefuel in the pressurizing chamber 14 is pressurized and the high pressurefuel is supplied to the fuel distribution pipe 20.

A spring seat 22 and a lifter guide 24 are stacked upon each other atthe lower side of the cylinder body 4. An oil seal 26 is attached to theinner surface of the spring seat 22. The oil seal 26 is generallycylindrical and has a lower portion 26 a that slidably contacts theperipheral surface of the plunger 12. Fuel leaked from a space betweenthe plunger 12 and the cylinder 4 a is stored in a fuel storing chamber26 b of the oil seal 26 and returned to a fuel tank T via a fueldischarge passage (not shown), which is connected to the fuel storingchamber 26 b.

A lifter 28 is accommodated in the lifter guide 24 slidably in the axialdirection. A projected seat 28 b is formed on an inner surface of abottom plate 28 a of the lifter 28. A lower end portion 12 a of theplunger 12 engages the projected seat 28 b. The lower end portion 12 aof the plunger 12 is engaged with a retainer 30. A spring 32 is arrangedbetween the spring seat 22 and the retainer 30 in a compressed state.The lower end portion 12 a of the plunger 12 is pressed toward theprojected seat 28 b of the lifter 28 by the spring 32. The pressingforce from the lower end portion 12 a of the plunger 12 causes thebottom plate 28 a of the lifter 28 to engage a fuel pump cam 34.

When the fuel pump cam 34 is rotated in cooperation with the rotation ofthe engine E, a cam nose of the fuel pump cam 34 pushes the bottom plate28 a upward and lifts the lifter 28. In cooperation with the lifter 28,the plunger 12 moves upward and narrows the pressurizing chamber 14.This lifting stroke corresponds to a fuel pressurizing stoke performedin the pressurizing chamber 14.

The electromagnetic spill valve 10 facing the pressurizing chamber 14 isclosed at a proper timing during the pressurizing stroke. In thepressurizing process, prior to the closing of the electromagnetic spillvalve 10, the fuel in the pressurizing chamber 14 returns to the lowpressure side fuel tank T via a space between a seat 10 b and a poppetvalve 10 a of the electromagnetic spill valve 10, a fuel passage 10 c, agallery 10 d, and a low pressure fuel passage 35. Therefore, fuel is notsupplied from the pressurizing chamber 14 to the fuel distribution pipe20. When an electromagnetic circuit in the electromagnetic spill valve10 causes the poppet valve 10 a to come into contact with a seat 19 b,the low pressure side fuel tank T and the pressurizing chamber 14 aredisconnected (the state of FIG. 4). As a result, the pressure of thefuel in the pressurizing chamber 14 increases suddenly and generateshigh pressure fuel. This opens the check valve 18 with the high pressurefuel and supplies the high pressure fuel to the distribution pipe 20.

When the cam nose of the fuel pump cam 34 starts to move downward, theurging force of the spring 32 starts to gradually move the lifter 28 andthe plunger 12 downward (intake stroke). When the intake stroke starts,the electromagnetic circuit in the electromagnetic spill valve 10separates the poppet valve 10 a from the seat 10 b and opens theelectromagnetic spill valve 10. This draws fuel into the pressurizingchamber 14 from the low pressure fuel passage 35 through the gallery 10d, the fuel passage 10 c, and the space between the poppet valve 10 aand the seat 10 b (the state of FIG. 3).

The pressurizing stroke and the suction stroke are performed repeatedly.The closing timing of the electromagnetic spill valve 10 during thepressurizing stroke is feedback controlled to adjust the fuel pressurein the fuel distribution pipe 20 at the optimal pressure for injectingfuel from the fuel injection valve 38. The feedback control is executedby an electric control unit (ECU) 36 in accordance with the fuelpressure in the fuel distribution pipe 20, which is detected by a fuelpressure sensor 20 a, and the running condition of the engine.

The cylinder body 4, the spring seat 22, and the lifter guide 24 form anintermediate member of the high pressure fuel pump 2 and are arrangedbetween the cover 6 (second clamping member) and the flange 8 (firstclamping member) in a stacked state. The electromagnetic spill valve 10has a base plate 10 f, and the base plate 10 f is attached to the cover6 by attaching bolts 10 e at a side opposite to the side where thecylinder body 4, the spring seat 22, and the lifter guide 24 areclamped.

The cylinder body 4, the spring seat 22, and the lifter guide 24 areclamped between the cover 6 and the flange 8 by clamping bolts 40 thatextends between the cover 6 and the flange 8. In the cross sectionalview of FIG. 3, the cross section at the right side of the axis of thehigh pressure fuel pump 2 differs from the cross section at the leftside of the axis. That is, the left cross sectional half and the rightcross sectional half are views taken at different cutting angles.Therefore, only one of a plurality of clamping bolts 40 is shown in FIG.3. FIG. 5 shows a cross sectional view of the high pressure fuel pump 2taken along the same cutting plane. As shown in FIG. 5, two clampingbolts 40 are arranged about the axis in a symmetric manner. In thisembodiment, two sets of clamping bolts 40 are arranged in a symmetricmanner around the cylinder body 4, the spring seat 22, and the lifterguide 24 to couple the cover 6 and the flange 8 to each other.

In the same manner, the attaching bolts 10 e for fastening theelectromagnetic spill valve 10 to the cover 6 are symmetrically arrangedabout the axis of the cylinder 12. In this embodiment, the base plate 10f of the electromagnetic spill valve 10 is attached to the cover 6 bytwo sets of the attaching bolts 10 e.

The entire high pressure fuel pump 2 is fixed to a cylinder head cover52, which serves as a supporting body, by a fastening bolt 54. Theflange 8 has clamping bolt holes 8 b, through which the clamping bolts40 extend, and fastening bolt holes 8 c, through which the fasteningbolt 54 extend. The fastening bolt holes 8 c are located closer to theperipheral portion than the clamping bolt holes 8 b. The fastening bolts54 are inserted in the fastening bolt holes 8 c in a direction oppositeto the direction of the clamping bolts 40 and screwed into screwapertures 52 a formed in the cylinder head cover 52. In this embodiment,two sets of fastening bolts 54 are arranged symmetrically about the axisof the cylinder 12. In this manner, the high pressure fuel pump 2 isprovided in the cylinder head cover 52. The bottom plate 28 a of thelifter 28 is exposed from a through hole 53 of the cylinder head cover52 and is engaged with the fuel pump cam 34 of the engine E. In thismanner, the plunger 12 reciprocates in the cylinder 4 a in cooperationwith the rotation of the engine E.

The high pressure fuel pump 2 of the present invention has the followingadvantages.

(1) In the high pressure fuel pump 2, the cylinder body 4, the springseat 22, and the lifter guide 24 are arranged between the cover 6 andthe flange 8. The cylinder body 4, the spring seat 22 and the lifterguide 24 are clamped by the clamping bolts 40, which extend between thecover 6 and the flange 8.

The electromagnetic spill valve 10 is attached to the cover 6 on theside that is opposite to the side where the cylinder body 4, the springseat 22 and the lifter guide 24 are clamped. The poppet valve 10 a ofthe electromagnetic spill valve 10 receives the reaction force (thearrow of FIG. 3) from the pressurizing chamber 14 when coming intocontact with the seat 10 b. Therefore, as shown in FIGS. 1(A) and 2(A),an increase in the axial force of the clamping bolts 40, which resultsfrom the reaction force received by the electromagnetic spill valve 10from the pressurizing chamber 14, is small in comparison to when theelectromagnetic spill valve 10 is arranged on the same side as thecylinder body 4, the spring seat 22, and the lifter guide 24.

When the base plate 10 f of the electromagnetic spill valve 10 receivesthe reaction force from the pressurizing chamber 14, the base plate 10 flifts the attaching bolts 10 e. This lifts the cover 6 and reduces theclamping force applied to the cylinder body 4, the spring seat 22, andthe lifter guide 24 is loosened. This decreases the reaction force thatresults from the clamping of the cylinder body 4, the spring seat 22,and the lifter guide 24. In this manner, even if the reaction force ofthe pressurizing chamber 14 is applied to the cover 6 by the fuelpressure pulsation produced during operation of the high pressure fuelpump 2, the reaction force resulting from the tightening of the cylinderbody 4, the spring seat 22 and the lifter guide 24 decreases. Therefore,the total reaction force is smaller than the sum of the two reactionforces.

Accordingly, the axial force change caused by the fuel pressurepulsation when the high pressure fuel pump 2 is operated decreases. As aresult, the initial axial force of the clamping bolts 40 decreases, anddistortion of each sealing surface of the cover 6, the cylinder body 4,the spring seat 22, the lifter guide 24 and the flange 8 and distortionof the form of the cylinder 4 a are prevented. This improves thedurability of the high pressure fuel pump 2.

(2) The reaction force of the pressurizing chamber 14 applied to theattaching bolts 10 e via the base plate 10 f of the electromagneticspill valve 10 acts in a direction for lifting the attaching bolts 10 e.Therefore, the reaction force resulting from the elastic deformation ofthe base plate 10 f near the attaching bolts 10 e decreased as the fuelpressure increases. The initial axial force of the attaching bolts 10 ealso decreases, and distortion of the sealing surface of theelectromagnetic spill valve 10 and the cover 6 is prevented.

Therefore, the present examples and embodiments are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims. The high pressure fuel pump of thepresent invention may be installed to a cylinder head of an engine.

1. A high pressure pump characterized by: a plunger; an intermediatemember having a cylinder for accommodating the plunger and apressurizing chamber communicated with the cylinder and including acylinder body for pressurizing fluid in the pressurizing chamber byreciprocating the plunger; two clamping members arranged on two sides ofthe intermediate member, wherein each of the two clamping members haselasticity; a first clamping bolt extending from a first of the twoclamping members to a second of the two clamping members to clamp theintermediate member with the two clamping members, the second clampingmember having a side facing the first clamping member where the firstclamping bolt meets the second clamping member, and the pressure of thefluid pressurized by the plunger being applied to the second clampingmember; a member for receiving reaction force from the pressurizingchamber when the fluid in the pressurizing chamber is pressurized,wherein the member for receiving the reaction force is attached to thesecond clamping member at a position for reducing the clamping forceapplied to the intermediate member by the clamping bolt and at a side ofthe second clamping member opposite to the side facing the firstclamping member, wherein the member for receiving the reaction forceincludes a base plate; and a second clamping bolt for fastening the baseplate to the second clamping member, wherein the first and secondclamping bolts are located at positions that are different from eachother in a direction perpendicular to a longitudinal direction of theplunger and close to each other when clamping, wherein the firstclamping member is a flange-like member and the second clamping memberhas a body portion and a protrusion portion that is protruded from thebody portion, and wherein the peripheral portion of the flange-likemember and the protrusion portion receive the clamping force produced bythe first clamping bolt.
 2. The high pressure pump according to claim 1,wherein the member for receiving the reaction force is arranged facingthe pressurizing chamber and functions as an electromagnetic valve forpressurizing the fluid in the pressurizing chamber by stopping movementof the fluid from the pressurizing chamber to a low pressure area. 3.The high pressure pump according to claim 1, wherein the fluid is fuelused for a cylinder injection type internal combustion engine.
 4. Thehigh pressure pump according to claim 3, wherein the first of the twoclamping members is attached to a cylinder head cover of the internalcombustion engine.
 5. The high pressure pump according to claim 3,wherein the plunger is driven by a fuel pump cam rotated in cooperationwith rotation of the internal combustion engine.
 6. The high pressurepump according to claim 1, wherein the reaction force from thepressurizing chamber acts in a direction for lifting the second clampingbolt by means of the base plate.
 7. The high pressure pump according toclaim 1, wherein the clamping force produced by the first clamping boltof the intermediate member and the clamping force of the second clampingbolt act in opposite directions along the axial direction of eachclamping bolt.
 8. The high pressure pump according to claim 7, whereinthe first clamping bolt of the intermediate member and the secondclamping bolt are arranged at positions separated from each other in theaxial direction.
 9. A high pressure pump characterized by: a plunger; anintermediate member having a cylinder for accommodating the plunger anda pressurizing chamber communicated with the cylinder and including acylinder body for pressurizing fluid in the pressurizing chamber byreciprocating the plunger; two clamping members arranged on two sides ofthe intermediate member, wherein each of the two clamping members haselasticity; a first clamping bolt extending from a first of the twoclamping members to a second of the two clamping members to clamp theintermediate member with the two clamping members, the second clampingmember having a side facing the first clamping member where the firstclamping bolt meets the second clamping member, and the pressure of thefluid pressurized by the plunger being applied to the second clampingmember; a member for receiving reaction force from the pressurizingchamber when the fluid in the pressurizing chamber is pressurized,wherein the member for receiving the reaction force is attached to thesecond clamping member at a position for reducing the clamping force,which is applied to the intermediate member by the clamping bolt, bylifting the second clamping member and at a side of the second clampingmember opposite to the side facing the first clamping member, whereinthe member for receiving the reaction force includes a base plate; and asecond clamping bolt for fastening the base plate to the second clampingmember, wherein the first and second clamping bolts are located atpositions that are different from each other in a directionperpendicular to a longitudinal direction of the plunger and close toeach other when clamping , wherein the first clamping member is aflange-like member and the second clamping member has a body portion anda protrusion portion that is protruded from the body portion, andwherein the peripheral portion of the flange-like member and theprotrusion portion receive the clamping force produced by the firstclamping bolt.